Electrical control apparatus



5mm 2, 1942. M. P. WHNTHER 2,285,246

ELECTRICAL CONTROL APPARATUS Filed March 19, 1941 2 Sheets-Sheet l LIQMMMM J a June 2, 1942. M. P. WINTHER ELECTRICAL CONTROL APPARATUS Filed March 19, 1941 2 Sheets-Sheet 2 Patented June 2, 1842 ELECTRICAL CONTROL APPARATUS .Martin P. Winther, Waukegan. IlL, aasignor to Martin P. Winther, as trustee Application March 10, 1041. Serial No. mar:

This invention relates to electrical control apparatus, and with regard to-certain more specific features to control apparatus for eddy-current slip clutches and the like.

Among the several objects oi the invention may be noted the provision of means for obtaining more accurate governing oi the speed or a slipclutch driven member in response to a given setting of a field rheostat, whether the rheostat is manually controlled, or controlled by incipient speed changes of the driven member of an eddycurrent clutch for the purpose of substantially constant-speed operation; the provision of apparatus of the class described which eliminates the errors that have heretofore been introduced by hysteresis eifects in the magnetic materials of the eddy-current clutch, particularly if it has a substantial mass of magnetic material, as is usual; and the provision of apparatus of the class described which is simple and reliable. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features or construction, and arrangements parts which will be exemplified in the structures hereinafter described, and the scope of the application 01' which will be indicated in the following claims.

In the accompanying drawings. in which is illustrated one of various possible embodiments of the invention,

Fig. 1 is a mechanical and wiring diagram;

Fig. 2 is a side elevation oi certain control parts;

Fig. 3 is a left elevation of Fig. 2;

Fig. 4 is a horizontal section taken on line l- -i of Fig. 2; and,

Fig. 5 is an enlarged vertical detail section oi a dash-pot, also shown on Figs. 2 and 3 but with its piston in mid position.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

In an eddy-current clutch, which is excited by direct current, and in cases where the speed of the eddy-current clutch must be closely regulated by a rheostat and must be held to the same value at the same corresponding rheostat position, it has been found, particularly where iron masses are of substantial sizes, that the hysteresis of the iron has caused a difilculty in accurately adjusting the speed in relation to rheostat position. Thus, for example, if a rheostat at a given position establishes a current of, say, 5 amperes in the excitation of a large clutch, and the speed has just been reduced from higher speed to 80% of that higher speed, then on returning to the given position from some lower speed, a current of 5 amperes will not result in 80% speed but it may result in only 60% speed.

This discrepancy is explainable by the supposition that the orientation of the molecules in the iron masses requires expenditure of energy. and the same value oi current willnot set up the same flux values it the current has been progressively reduced to said value instead of progressively increased to said value, and vice-versa. Although the rheostat has returned to the same setting and the amperes flowing are the same, the flux set up is not the same and therefore the torque transmitted by the clutch, and hence the speed developed'by the driven member of the clutch will not be the same in the case oi variable torque loads. This applies for example particularly to drives for fans where the torque varies as the square of the speed.

The invention corrects for the lag in the magnetization of the iron by correcting for hysteresis. This is accomplished by violently jolting or jarring the molecules in the iron by suddenly temporarily over or under exciting considerably in excess or in deficiency oi the value desired, the excess or deficiency being applied momentarily as the rheostat moves to its desired position. By means of this device, over excitation is temporarily and suddenly applied as the current is being built up so as to Jar the molecules into a final orientation which is desired for the constant value or current desired, and on the other hand, when the current is decreased the excitation is suddenly temporarily decreased below the desired value as the current is being reduced. In this wa the flux values finally set up by the current corresponding to any definite rheostat position are the same each time the rheostat travels to the same position, regardless of which way it approaches that position. In other words, this method eliminates the effect on smed of the hysteresis loop of the iron.

'Under the old conditions, the speed discrepancies and torque discrepancies could he plotted out in a loop which would be similar to the hysteresis loop. and the present invention may therefore be said to eliminate what may be called a speed or torque loop in plots of speed or torque against rheostat setting or current values.

United States Patents 1,982,461, dated November 2'7. 1934, and 2,050,479, dated August 11, 1936, describe constructions wherein a power driving element is coupled to a driven element through an eddy-current slip clutch, the field ,Windings of the clutch being energized from an electric circuit including a rheostat consisting of a stepped series of resistances and parallel stepped contacts respectively. These contacts are successively closed and opened by a speed-responsive mechanism which in response to incipient increase in speed of the driven member'tends to open the contacts serially, thus inserting resistance into the circuit step-by-step and reducing results in preventing further speed increase.-

Also, upon incipient decrease in speed, said speed-responsive mechanism tends serially to close said contacts, so as to short circuit the resistances step-by-step. Hence resistance is taken out of the circuit, whereupon the field coil is increasingly energized to increase the flux connection between the driving and driven elements so as incipiently to increase the speed.

Fig. 3 of Patent 2,050,479, particularly,shows the above-mentioned construction in its essentials. It is quite useful, but the present invent-ion improves it by eliminating the conditions of driven-element speed lag referred to rheostat position or current. It is to be understood however that the present invention is applicable also to hand-controlled rheostats by substituting manual control for speed-responsive control.

Referring now more particularly to Fig. 1 herein, there is shown at numeral I a driving motor for the eddy-current inductor drum 3 of an electro-magnetic slip clutch C. This clutch has magnetic poles 1 upon its driven member I5. On the poles are field windings 9 energized from slip rings II and I3. The driven element I5, in the present example, is shown as driving a. blower fan I1 which by way of example may be for combustion control purposes. A speed-responsive governor is shown generally and diagrammatically at I9, arranged so that its fly weights 2!, upon increase in speed of the driven member I5,

draw over a yoke 23 against the action of springs 25 so as to move a lever arm 21 on a control shaft 29. When the speed of the driven member 55 incipiently increases, the yoke 23 is pulled to the right to move the lever arm 21 counterclockwise. This causes step-by-step opening of spring mounted contacts 3| which are connected in parallel with a series of resistances 33, so that said resistances 33 are successively introduced into the circuit which energizes coils 9. The energizing circuit referred to runs from point through point 31, points 39 and ll of a normally closed make-and-break relay switch NC, slip ring II, coils 9, slip ring I3, points 43 and 45 of a hand switch HS, battery 41, point 49, and then through such of the resistances 33 as are not short circuited by contacts 3|.

When the speed of the driven member I5 incipiently decreases, the same circuit is traversed by the current, except more of the resistances 33 are short circuited by more of the contacts 3| in response to movement of the collar 23 to the left, and clockwise rotation of the lever 21. It should here be pointed out that the showing of the operating connection or lever 25 between shaft 29 and the contacts 3| is diagrammatic, and that in practice it may be any applicable linkage, such as, for example, the linkages in U. S. Patent 1,982,461 or 2,220,007, or others.

From point 31 is a connection to a point 5| of a normally open make-and-break relay switch NO. The other point 53 of said switch NO connects with point 49 via point 55, Thus it will be seen that the normally open switch NO is in parallel across the resistances 33 and when the switch NO is closed these resistances are short circuited. Such a condition suddenly places the full energizing current on the coils 9. On the other hand, if the relay switch NC is opened,

then the circuit to the coils 9 is completely and suddenly deenergized. If desired, a relatively large resistance could be connected across points 39, ll so that the resistance upon opening switch NC would not be infinite.

The relay switches NC and NO have their operating coils 53 and 69 energized from a transformer 51. An acceleration switch 59 which is normally spring-opened, controls the circuit 5| which energizes the coil of the relay switch NO. A normally spring-opened switch 33 controls the circuit which energizes the coil of the relay .swltch NC.

The switches 59 and 53 are under control of the motion of the lever 21. While lever 21 has been diagrammed only broadly in Fig. 1, it is actually as shown in detail in Figs. 2, 3'and 4. It functions, not only to operate shaft 29, but also switches 59 and 63, which are mounted thereon, as will appear.

Referring to Figs. 2-5, the rheostat control lever 21 controls the shaft 29 which in turn controls suitable contacts in control box 61. The shaft 29 .is shown in Figs. 2-4, and also lever 21, but the linkage corresponding to item 29 in Fig. l is within control box 51 and'further description is unnecessary.

As shown in Figs. 2-4, lever 21 is fastened to the shaft 29 by set screw 30. Concentric with the shaft 29 and extending from the lever 21, and rotary therewith, is a pin 69. This supports an independently rotary lever 1| on bearings 13. Bearings 13 assure free relative movement.

At 15 and 11 are shown two pins which slide through lugs 19 and 8|, respectively, on the lever 21. These pins have adjustable heads 83 and 85, respectively. These heads are arranged in connection with the lugs 19 and 9| so that opposite heads 81 and 89, respectively, on the pins 15 and 11 will be flush against opposite sides of a lever TI. This is when compression springs 9I and 93, respectively, are extended. Thus there is a resilient driving connection between the lever 21 and the lever 1i, through spring-pressed pins 15 and 11. Limiting-stops I51 and I69 prevent excessive spring deflection. l

The lever 1I (pivoted on 69) is used to close the normally open switches 59 and 53 by relative lagging movement with respect to the lever 21 when the latter starts to move. This is done by carrying the switches 59 and 63 in an extended box portion attached to the control lever 21. The cover of this box is shown as being removed, for clarity. The switches 59 and 33 are of the variety called micro-switches. These are characterized by a bias to one position or another and in this case each biases toward open position by suitable internal spring means. These are also characterized by closing snap action in response to a very minute application of operating movement, to their operating elements. Their bias opening action is also of the snap variety. Since such switches are known, further details are not necessary.

Thus, when the arm 21, in response to undesired speed increase, moves to the right in Fig. 1 (up in Fig. 2), a speed-decrease correction is desired. This occurs by reason of the opening of the contacts 3I which introduces into the exciting circuit for 9, the desired amount of increased resistance 33 to correct the speed increase. In other words, the clutch coupling slips more. However, since the initial movement or acceleration of the lever 21 (up in Fig. 2) is relative to stationary lever 1|, the latter is engaged by the button I55 of the micro-switch 63 temporarily to close that normally open switch. This temporarily opens the normally closed relay switch NC and the exciting circuit tor the coils 9. After the lever 21 reaches its adjusted position, spring 99 (which has been compressed) pushes the previously lagging lever 1I into the center position with respect to arm 21, whereupon the micro-switch 99 returns to its normally open condition. This permits the switch NC to reclose, whereupon the circuit will be excited ac-,

short out increasing amounts of resistance 99.

This increases the excitation of the coils 9 for tightening the clutch connection, which causes pick-up of speed of the driven member I9. As the lever 21 (Fig. 2) moves down the lever 1i lags temporarily to become engaged by the button i69 oi the upper micro-switch 99. Microswitch 99 temporarily closes normally open relay switch NO. This temporarily short-circuits all of the resistances 99 to give a sudden high degree of excitation to the coils 9. When lever 21 stops the spring 9i causes follow-up of lever II and reopening of switches 99 and NO, whereupon the circuit will be excited according to the amount of newly adjusted resistance 99. Iithis results in eliminating the underspeeding further action is unnecessary, but it not, the same sequence 01 events may occur again, or several'times before constant conditions result.

Over-excitation or under-excitation, as the case may be, of the coils 9 is only temporary and in the nature of a current for violently jarring the molecules of the iron. Hence the molecules take up ultimately desired adjusted positions corresponding to a given current, instead of different positions which depend upon whether the adjusted degree of magnetization was arrived at from higher or lower values.

Referring now to the resiliently coupled damping mechanism coupled with lever 1I (Figs. 2-4), the left-hand end of the lever H is pivoted at 91 to a link 99 which has a contact engagement with a link IIII at fiat pads I99. The links 99 and IIII are pinned at I09 and I91, respectively, to a bridle link I09. This forms a double-rocking hinge between 99 and IIII. When 99 raises it rocks temporarily on I III at heel IIIII, provided resistance occurs at I2I, where link IN is resiliently held, as will appear. when 99 descends rocking is temporarily at heel I02. Link 99 has an extension III and link IIII has an extension II3. These extensions III and II9'have extension pins I I9 and I I1, respectively, between which react springs II9 for the purpose of biasing the links 99 and IM together at the pad portions I03.

Thus upon lowering or raising 99, the angle I2I may be resiliently increased or decreased but tends under non-moving conditions to maintain the value shown. in view of the springs H9.

The upper outer end of the link IIII is pivoted at I2I to a clevis I29 of a dash-pot arrangement shown generally at I29 (detailed in Fig. with its piston down). Link IIII is also pinned at I21 to a link I29 which is pinned at Hi to a rocker I39. The rocker I93 is pinned at I99 to the enclosure I31 for the rheostat and associated parts.

The right-hand end of the rocker I99 carries a counterbalance I99 so that the net weight oi the connecting parts between the lower and upper pins 91 and III will not be applied to rotating the lever 1I. That is to say. the lever H is to maintain a neutral position and to move only in response to motion of the lever 21.

The clevis I29 is threaded on a head III and locked there by a nut I99. The head III is ad- Justably threaded into a hollow piston rod I99 and is held In any adjusted position by a Jam nut I41.

The hollow piston rod I49 reaches through a head I99 into a stationary dash-pot cylinder III which is also fastened to the side oi the box I91. At its inner end, the piston rod I49 carries a piston I99 which has an opening I99 therethrough controlled by a needle valve I91. The needle valve extends from the adjustable head I and may be externally adjusted. An opening I99 in the hollow piston rod I49 permits intercommunication between the opposite sides of the piston H9, under control of the needle valve I91. A breather tube is shown at I. In operation the cylinder I91 is filled to its designed capacity with. dash-pot oil, and any motion up or down of the piston rod encounters the damping resistanoe oi flow through the openings I99 and I99, as throttled by the needle valve I91.

Operation oi the linkage between the lever .1I and the dash-pot is as follows:

when the lever 71 is rotated clockwise, the pin 91 is driven toward the pin I21. This tends temporarily to angle together the links 99 and IIII by rocking on heel 899 and by rotation of link "on pin M9. This scissors action is against the action of springs H9. Then the springs II9 tend again to angle the links 99 and NI back to angle I2I with pads M9 flush. Reaction tor the purpose comes from spring III acting on lever II. This necessitates rising action of the pin I21 against resistance of the dash-pot I29. The dashpot slowly permits the action 01 springs I I9 to proceed until the angle I2! is again assumed in a new and lifted position of both links 99 and IIII.

On thevother hand, if the lever ll is rotated counterclockwise, the pin 91 moves downward away from the pin I2 I, thus depressing the link 99 so that the link I9I first rotates on pin I91 and heel I92, temporarily to increase the angle I2I against the pull of springs II9. Then the dashpot permits the pin III to proceed down by the action of springs H9 in bringing together the links 99 and III to the angle I2I shown. Spring 99 provides the reaction.

In Fig. 2, a dotted-line alternate position of parts indicates an extreme limiting counterclockwise condition oi the lever H and the solid lines a mid position or parts. It is to be understood that the parts are in static, and not moving, condition, both in the solidand dotted-line positions, and also that the mid position of the piston I99 in Figs. 2 and 3 corresponds to the solid-line, mid positions of the parts exterior to the cylinder I9I.

The balanced scissors linkage attached to lever H at 91, and attached to the dash-pot at I21,

provides damping effects for lever 1I. .Since the lever 21, through spring-pressed pins 9I and 99 causes rotation of the lever 1|, the relative motion between these levers upon movement of 21 causes temporary closing ofone or the other of the normally open switches 99 or 99, depend- Assume first that for some reason, as by unloading, the driven member I! of the clutch C accelerates. This will cause the centrifugal governor to move the lever 21 to the right in Fig. 1,

lay switch NC to open. For an instant the coils 9 are deenergized, thus instantly demagnetizing the poles 1 and eddy-current member 3 before remagnetization at the desired adjusted lower value. At this time,- links 99 and llll raise while angle I21 temporarily reduces due to temporary delaying action of the dash-pot I25. Spring 99 reopens switch 63.

n the other hand, should the governor in response to speed decrease rotate the lever 21 to the left (clockwise) in Fig. 1 and down in- Fig. 2, then the lag of the lever 1| would be taken up by the spring 9| and the switch 59 would temporarily instantaneously close to instantaneously close the normally open relay switch NO. This temporarily short circuits the resistances 33 so as to energize the coils 9 to a maximum, after which the spring 9| resets'the lever 1| on center with respect to the lever 21. This reopens the switch 59 and also switch N0, whereupon the magnetizing current'ialls oil, thus permitting the magnetization to come down to the value desired from an upper value.

In view of the above, it will be seen that, whenever it is desired to adjust speedby decreasing magnetization, the first thing that occurs is to cut oil the magnetization altogether under practically open-circuit conditions, and thento adjust magnetization to the proper value; whereas if it is desired to increase the speed, this is done by first instantaneously magnetizing to the maximum, under practically short-circuit conditions, and then adjusting the magnetization to the desired value.

It should be noted that the degree of adjusting motion of the lever 21 for the above purpose is small as an adjustment is consummated, and that the large throw which is'indicated for this lever is for the purpose of providing a wide range of positions at which the action described may take place. The device has the same characteristics at whatever speed the governor is controlling. It will 01 course be understood that the speed at which control is efiected for the driven member J5 may be changed by adjustment of the governor springs. This needs not to be gone into herein because means for adjusting such springs are known.

For best results the temporary over or underexcitation should be considerably in excess or deficiency of the final value of exciting current desired, and the temporary values should be quickly and suddenly increased and decreased. Thus the short circuiting of resistances 99 by switch NO provides an instantaneous rush of a substantially higher current to the full extent of which the battery 41 is capable (in view of its line resistance) without resistances 33. Also, the opening of switch NC inserts a very high resistance to flow of current. The nature of the result in the magnetic members is strongly to reorient the magnetic properties oi! the device.

It is preferable that the springs 9| and 99 be pre-compressed when the heads 91 and 89 are in proper position against the lever 1|, so that an eiiective force is obtained from aaeaaee and 99 for assuring final setting of the linkage between points 91 and. I2! into its position for angle l2! shown, whenever an adjustment is made. Ultimate limit stops I61 and "9 between the lever 1| and the lever 21 limit the amount 0! compression that may be placed in the springs 9| and 99 respectively.

In view 01 the above. it will be seen that the invention consists of the rheostat 61 which, through a suitable linkage, operates with the control lever 21, there being a lost-motion connection between the control lever 21 and the contact or switch lever 1| which, upon movement of the control lever 21, results in temporarily closing one or the other of the switches 59- or 63; to-

gether with damping means I25 and a resilient connection between the damping means I25 and the contact lever 1|.

In the above disclosure, the theory of operation is presented with the understanding that other theories may be applicable. In any event,

the structure brings-about the ultimate ends of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. In an eddy-current clutch, an eddy-current member, a magnetic field member cooperating therewith, means for exciting said field member comprising an electric circuit, a rheostat for controlling said circuit and consequently the excitation of the field member, and means responsive to adjusting movement of the rheostat for temporarily reducing the value of current in said circuit below the requirement at the final position of the rheostat when the rheostat is adjusted for field decrease, and for temporarily increasing comprising a control member, a switch-operating means having lost motion engagement with said control member and operating the switches, the switch in series responding to lost motion in one direction substantially to increase resistance in the circuit beyond that which normal adjustment of the rheostat accomplishes in adding resistance to th circuit, and the switch in parallel responding to lost motion in the opposite direction substantially to decrease resistance in the circuit below that which normal adjustment of the rheostat accomplishes in subtracting resistance irom the circuit.

3. In apparatus or the class described, a field member, a circuit for exciting said field member, a rheostat controlling circuit resistance to control the excitation by said circuit, make-andbreak switches respectively in series and parallel with the rheostat, means for moving the rheostat comprising a control member, a switch means the springs Si having lost motion engagement with said control member and operating the switches, the switchin series responding to lost motion in one direction substantially to increase resistance in the circuit beyond that which normal adjustment of the rheostat accomplishes in adding resistance to the circuit and the switch in parallel responding to st motion in the opposite direction substantially to decrease resistance in the circuit below that which normal adjustment of the rheostat accomplishes in subtracting resistance irom the circuit, damping means, and a resilient connection between the switch member and the damping means. 1

4. In apparatus of the class described, a field member, a circuit for exciting said field member. a rheostat controlling circuit resistance to control the excitation by said circuit, make-andbreak switches respectively in series and parallel with the rheostat, means for moving the rheostat comprising a control member, a switch means having lost motion engagement with said control member and operating the switches, the switch in series responding to lost motion in one direction substantially to increase resistance in the circuit beyond that which normal addustment oi. the rheostat accomplishes in adding resistance to the circuit and the switch in parallel responding to lost motion in the opposite direction substantially to decrease resistance in the circuit below that which normal adjustment of the rheostat accomplishes in subtracting resistance from the circuit, resilent means between the control and switch members for taking up said lostmotion after an adjustment, damping means, and a resilient connection betweenthe switch member and the damping'means.

5. Eddy-current apparatus comprising an eddycurrent member, a field member, a circuit for exciting the field member, a control rheostat providing diii'erent values of exciting current for diiierent rheostat positions, and means responsive to initial movement or the rheostat to temporarily decrease the current value below that efiected at a curent-decrease setting of the rheostat, or to temporarily increase the current value above that eilected at a current-increase setting of the rheostat.

6. Eddy-current apparatus comprising a driving member, a driven member, one of said members consisting oi an eddy-current member and the other a field member, a circuit for exciting the field member, a control rheostat providing diflerent values of current in response to opposite rheostat movements, and means responsive to initial movement of the rheostat in current decrease direction temporarily to decrease the current value below that at the final current-decrease setting and means responsive to initial movement of the rheostat in current-increase direction temporarily to increase the current value above that effected at the final currentincrease setting.

'7. In an eddy-current clutch, a driven member,

a magnetic field coil, means responsive to the speed oi the drivm member for decreasing excitation when speed incipiently increases, and for increasing excitation when speed incipiently decreases, and means responsive to initial movement of the speed-responsive member in a direction to increase current temporarily to apply substantially higher current, and responsive to initial movement or the speed-responsive memtemporarily cause current fiow through said circuit which is more than that flowing at. the higher-current position, and means temporarily responsive to movement of the rheostat from the higher current position to the lower-current po-' sition for temporarily decreasing the flow of current to a value below that corresponding to the lower-current position.

9. In an eddy-current clutch, a magnetic driving member, a magnetic driven member, a magnetic field coil providing a magnetic field in one 01' said members i'or inducing eddy-currents in the other member, adjusting means responsive to the speed of the driven member for decreasing excitation of the coil when speed incipiently increases, and for increasing excitation when speed incipiently decreases, and means responsive to initial and incipient movement or the speed-responsive member in a direction to increase current, instantaneously and temporarily to apply a rush of substantially higher current, and responsive to initial movement oi the speedresponsive member in a direction to decrease current instantaneously and temporarily to insert a very high resistance to fiow of current, whereby temporary strong reorientations of magnetic properties are obtained in said magnetic members upon each incipient adjusting action of said adjusting means.

10. In an eddy-current clutch, a driving member, a driven member, at least one of said members being magnetic, a magnetic field coil producing a magnetic field intrlinking said members, adjusting means for gradually increasing and decreasing excitation of. the coil and automatic means adapted temporarily and suddenly greatly to exceed the value or the increase or decrease in said excitation, as the case may be, whereby complete reorientation of the magnetic properties of the magnetic member is eflected in response to each adjustment.

l1. In an eddy-current clutch, a driving member. a driven member, at least one or said members being magnetic, a magnetic field coil producing a magnetic field interlinking said members, adjusting means for gradually increasing and decreasing excitation of the coil respectively for incipiently increasing and decreasing the speed 01' the driven member, and automatic means responsive to incipient movement of the adjusting means adapted temporarily and sudsame value.

MARTIN P. WINTHER. 

